Rod-shaped body

ABSTRACT

The invention relates to a rod-shaped body (1) comprised of one or more filaments (2) and of a non-ferromagnetic matrix material (3). The matrix material (3) surrounds the filament(s) (1) and/or adheres them to one another. The rod-shaped body is also comprised of a dopant consisting of particles that generate magnetic resonance tomographic artifacts that is introduced into the matrix material (3). Rod-shaped bodies of this type can be used to construct guide wires, catheters and other instruments to be used in minimally invasive surgical interventions.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of co-pending U.S. patentapplication Ser. No. 16/225,637, filed on Dec. 19, 2018, now U.S. Pat.No. ______, which is a divisional application of U.S. patent applicationSer. No. 14/710,734, filed on May 13, 2015, now U.S. Pat. No.10,172,537, which is a Continuation-in-Part application of U.S. patentapplication Ser. No. 11/993,658, filed on Nov. 23, 2009, now U.S. Pat.No. 9,038,639, which in turn claims priority to PCT Application No.PCT/DE2006/001094 filed on Jun. 26, 2006, which in turn claims priorityto German Patent Application No. DE 10 2005 030 472.9 filed on Jun. 28,2005, the contents of all applications are hereby incorporated byreference herein.

BACKGROUND OF THE INVENTION Technical Field

The invention relates to the field of devices, in particular guidewiresand catheters, needed for minimally invasive interventions.

Related Art

Minimally invasive interventions in the human body require guidewiresand catheters. These are available in a multitude of forms, sizes,configurations and mechanical characteristics for procedures guided byX-ray imaging.

These catheters and guidewires are not applicable to magnetic resonancetomography (MRT)-guided procedures as they usually contain metals. Thisleads to artifacts which makes evaluation of the images difficult oreven impossible. Furthermore, this conceals the risk of inductiveheating in the magnetic field leading to a potential risk to thepatient.

Three essential requirements have to be fulfilled by devices to makethem suitable for use in MRT:

-   -   1. They must not contain any long metal parts, e.g. metal fabric        for catheter reinforcement or wire cores for guidewires.    -   2. They need to be visible over optimally their full length in        the MRT image so that the position of the device is clear in        relation to the organ(s).    -   3. As the local resolution in real-time MRT currently does not        allow a direct imaging of catheters and guidewires, clearly        visible effects have to be generated along the length of the        device.

Such effects on the one hand should be strong enough to render thedevice well visible in the MRT image but on the other hand weak enoughnot to make important structures in the vicinity unidentifiable.

The strong magnetic field of a magnetic resonance tomography makes theabsence of any ferromagnetism a precondition for the use of deviceswithin this equipment. This excludes e.g. many standard catheters whichcan be attracted and misguided by the strong magnetic field. Materialssolely composed of polymers fulfill the prerequisite of absence offerromagnetism.

The minimal size of devices used for intervention such as guidewires orcatheters causes a special problem for application in magnetic resonancetomography and especially for rapid imaging. The faster imaging is donein MRT the lower is the local resolution. In order to make visible sucha small item as a catheter which shows up as a dark object due to therelative lack of hydrogen protons, appropriate high-resolution and thusslow imaging is necessary. Furthermore, it is very difficult to makevisible such a small item in the usually prepared layer thickness ofaround 10 mm so that on the one hand it is positioned within therecorded layer and on the other hand it does not become invisible due topartial volume effects.

A solution to this problem resides in markers which lead to a localextinction of the signals in the MRT image and therefore allow easieridentification and visualization of the device. For this purposegenerally materials which possess a susceptibility (magnetizability)different from water are suitable. The markers have to be appliedlocally in order to avoid dependence of the marker on the orientation ofa device in the main magnetic field. Rare earths which are used as MRTcontrast agents have been used for this purpose in higherconcentrations. They have been applied or introduced, both locally asmarkers as well as for catheter fillings to obtain better visibility ofdevices in the MRT.

A major disadvantage of these substances used so far as local markersresides in their rather high mass required to achieve a sufficientmarking effect in the MRT. This is reflected e.g. in the fact that muchmore complicated techniques for conducting current along a wire withinthe device, or which mount micro-inductors on the catheter, have beendeveloped although resultant safety issues such as heating from theradio frequency field have not yet been resolved at all. These heatingeffects occur when electric conductors such as metals are exposed to theradio frequency field over a longer distance in the MR tomograph. Ifresonance occurs, a summation of the irradiated radio energy over astanding wave results, with the possible consequence of a substantialheating of the conductor.

Known single-stranded homogenous non-metal materials exhibit majordisadvantages of their material characteristics in comparison to commonmetal cores regarding stability, flexibility and elasticity, e.g.,materials with high stability mostly possess low flexibility and/orelasticity. Consequently it has not been possible to date to replace thecommon metal core by an MRT compatible and visible material.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide MRT-compatibledevices, especially a catheter and a guidewire, which do not containlonger coherent metallic parts and thus do not suffer from the risk ofinductive heating. On the other hand the device shall be visible inappropriate MRT sequences over its complete length along and across themain magnetization without having body structures in the vicinity of thedevice made unrecognizable as a result of artefacts. A further object ofthis invention is that of providing MRT-compatible devices which do notsuffer from any limitations in material characteristics and handlingproperties as compared to currently known devices.

As a solution to this problem a rod-shaped body (“rod”) is suggestedwhich is composed of one or more non-metallic filaments and anon-ferromagnetic matrix material wherein the matrix material enclosesand/or agglutinates the filament(s), and wherein a doping by particlesproducing artefacts in magnetic resonance tomography is included intothe matrix material. The combination of the matrix material with thenon-metallic filament(s) results in an unexpectedly simple manner inmetal-like stiffness, flexibility and elasticity characteristics.

The filaments forming the rod-shaped body can be produced easily andcost-efficiently, with adequate stability and the ability to transmitcompressive and tensile force and torques. By doping of the matrixmaterial which is either necessary for enclosure of a single filament oragglutination of several filaments, a simple and efficient method hasbeen developed to visualize the rod-shaped body in the MRT and at thesame time to allow handling according to current standards.

The actual devices such as catheters, guidewires, etc. are constructedfrom these basic elements as described below. Advantageous developmentsof the invention are the subject of the dependent claims.

It is especially advantageous if the filaments are made of plasticand/or glass fibre. Such filaments can be easily and cost-efficientlyproduced with great length and a wide variety of cross-sections anddiameters. Especially glass fibre has minimal elongation, makingpossible very direct transmission of force and momentum.

The matrix material may advantageously be made of epoxy resin. Epoxyresins are available with a wide range of properties and machines fortheir processing are well-developed.

The rods can be continuously doped along their longitudinal axis withparticles generating artefacts in magnetic resonance tomography. Thismakes the rod well visible in the MRT over its entire length.

For some applications, however, it may be preferred to dope the rod in adiscontinuous manner, particularly in sections along its longitudinalaxis, with particles generating artefacts in magnetic resonancetomography. This especially applies to the tips of the rods which needto be exceptionally visible in some cases.

Within the rods the filaments can be arranged in parallel. This supportsespecially simple processing.

The filaments also can be arranged braided with each other, woven,cross-linked, twisted or coiled in especially preferred embodiments inorder to realize certain favoured characteristics, especially mechanicalproperties.

It is advantageous if the mass of a single particle is in the range ofmicrograms to nanograms and, due to the minimal amount in relation tothe matrix material, does not substantially influence the outer shape,stability and the torquing characteristics of the rod.

Typically preferred sizes of the rods are in the diameter range ofbetween 0.005 and 5 mm, preferably between 0.1 and 1 mm.

A cylindrical composite body (“cylinder”), particularly a guidewire, isconstructed from the described rods in such a manner that at least onerod is enclosed by a non-ferromagnetic matrix material or several rodsare enclosed and/or agglutinated by a non-ferromagnetic matrix material.

In this way cylinders of widely varying geometries and mechanical aswell as MRTrelated characteristics can be easily and cost-efficientlyconstructed with one and the same element (the rod) and the matrixmaterial.

The cylinder may e.g. most simply be built from rods of the samediameter or—in another embodiment—from rods of different diameters. Thelatter embodiment in particular may have two rods of smaller diameterarranged around a first rod. The individual rods can—similar to thefilaments as before—be arranged braided with each other, woven,cross-linked, twisted or coiled.

In a particularly preferred embodiment the cylinders contain rods withdifferent magnetic resonance tomographic properties. For instance thesame cylinder (e.g. as a guidewire) can be visualized equally well indifferent MRT sequences (e.g. for

specific visualization of fatty tissue, muscle tissue, etc.).

It is advantageous to cover the outer surface of the cylinder with ahydrophilic coating thus making it biocompatible.

It is however also possible to construct other devices from thedescribed rods, particularly a tube-shaped composite body (“catheter”).This is composed of at least one rod which is enclosed by anon-ferromagnetic matrix material and/or several rods bonded togetherand/or enclosed.

In an embodiment of the catheter this is comprised of several rods whichare embedded in a radial distribution in the periphery of its wall.Especially for achieving symmetrical properties these can be embedded ina regular radial distribution.

For the same reason the rods forming the catheter can possess the samediameter. In special cases however rods of different diameter can alsobe used.

Similarly to the cylinders and guidewires, in the case of the catheterrods can be arranged braided with each other, woven, cross-linked,twisted or coiled in the catheter and can possess different magneticresonance tomographic properties. The outer surface of the catheter canbe hydrophilically coated.

Besides the above described devices other devices can be constructedfrom rod-shaped bodies and the matrix material in similar manner, e.g.Dormia baskets.

Preferred embodiments of the invention are described below with the aidof the enclosed schematic drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a doped rod of the present invention.

FIG. 2 shows a cylindrical composite body (guidewire).

FIG. 3 shows a tube-shaped composite body (catheter).

FIG. 4 shows a cross-section through a doped rod.

FIG. 5 shows the tip of a guidewire.

DETAILED DESCRIPTION OF THE INVENTION

The rod 1 and section of a rod respectively shown in FIG. 1 consist ofan elongated glass fibre filament 2 which is embedded in epoxy resin 3as the matrix material. The rod 1 can be produced using commontechniques, particularly by extrusion so as to be virtually endless.After extrusion it may be cut to the length required for furtherprocessing.

Particles producing magnetic resonance tomographic artefacts, e.g.nanoparticles, —not shown—are included in the epoxy resin. These arehomogenously distributed in the matrix material so that a rod 1homogenously doped along its longitudinal axis results.

As shown in FIG. 4 instead of one filament also several filaments 4, 5can be arranged in a rod-shaped body 1. In the example shown this is arather thick filament 4 and arranged around this are rather thinfilaments 5. All filaments 4, 5 are agglutinated with and encompassed bythe epoxy resin 3.

In FIG. 2, a cylindrical composite body 6 and a section of this areshown. The lengthwise extension can be significantly longer, amountingto e.g. several meters with a diameter of e.g. 0.1 mm.

The cylindrical composite body 6 is constructed from several rods 1which are agglutinated and enclosed by a matrix material 7, e.g. anepoxy resin. This matrix material 7 is, in contrast to the matrixmaterial 4, not doped with particles producing magnetic resonancetomographic artefacts. The visibility of the cylindrical composite body6 in the MRT relies solely on the visibility of the embedded rods 1. Inthe depicted embodiment, rods 1, 8, 9 with different dopings areincluded so that, depending on the sequence, different rods 1, 8, 9become visible in the MRT.

In the same way, as shown in FIG. 3, a tube-shaped composite body 10 canalso be constructed (once again only a section is shown here).

The tube-shaped composite body 10 is similarly constructed from a shellmaterial 15 and several rods 1, 8, 9 with different doping. All rods areevenly distributed around 10 the periphery of the tube-shaped compositebody 10.

The cylindrical composite body 6 as well as the tube-shaped compositebody 10 can be covered with a hydrophilic coating, which is not shown.

The ends of the cylindrical and tube-shaped composite bodies 6, 10 canbe treated in an appropriate manner, e.g. rounded, polished or capped.As shown in FIG. 5, particularly the inner rod 12, in a guidewire 11with an inner rod 12 and radially distributed outer rods 13, can beshorter than the outer rods 13. These are brought together and form atip 14 (arrangement of the rods 12 and 13 as displayed in thecross-sections A-A and B-B respectively).

That which is claimed is:
 1. A rod-shaped body comprising: one or morenon-metallic filaments; and a non-ferromagnetic matrix material and amultiplicity of doping particles, wherein the non-ferromagnetic matrixmaterial encloses and/or agglutinates the one or more non-metallicfilaments, wherein the multiplicity of doping particles are distributedin the non-ferromagnetic matrix material, and wherein the dopingparticles generate magnetic resonance tomography artefacts.
 2. Therod-shaped body according to claim 1, wherein the rod-shaped body is arod-shaped body for manufacturing a medical instrument, wherein themedical instrument is a catheter or a guidewire.
 3. The rod-shaped bodyaccording to claim 1, wherein the one or more non-metallic filamentsconsist of plastic and/or glass fibre.
 4. The rod-shaped body accordingto claim 1, wherein the non-ferromagnetic matrix material comprisesepoxy resin.
 5. The rod-shaped body according to claim 1 wherein thedoping particles are included continuously along the longitudinal axisof the rod-shaped body.
 6. The rod-shaped body according to claim 1,wherein the doping particles are included discontinuously along thelongitudinal axis of the rod shaped body.
 7. The rod-shaped bodyaccording to claim 1, wherein the one or more non-metallic filaments arearranged in parallel.
 8. The rod-shaped body according to claim 1,wherein the one or more non-metallic filaments are braided with eachother, woven, cross-linked, twisted or coiled.
 9. The rod-shaped bodyaccording to claim 1, wherein a single particle of the multiplicity ofdoping particles has a mass in the range of micrograms to nanograms and,due to a minimal amount in relation to the non-ferromagnetic matrixmaterial, does not substantially influence outer shape, stability ortorquing characteristics of the rod-shaped body.
 10. The rod-shaped bodyaccording to claim 1, having a diameter in the range of between 0.005 mmand 5 mm or between 0.1 and 1 mm.
 11. A cylindrical composite bodyconsisting of: at least one rod-shaped body consisting essentially of:one or more non-metallic filaments; a non-ferromagnetic matrix material,wherein the non-ferromagnetic matrix material encloses and/oragglutinates the one or more non-metallic filaments; and a multiplicityof doping particles distributed in the non-ferromagnetic matrixmaterial, wherein the doping particles generate magnetic resonancetomography artefacts; and a non-ferromagnetic shell material, whereinthe shell material encloses and/or agglutinates the at least onerod-shaped body.
 12. The cylindrical composite body according to claim11 consisting of several rod-shaped bodies having the same diameter ordifferent diameters.
 13. The cylindrical composite body according toclaim 11 consisting of several rod-shaped bodies where a firstrod-shaped body of the at least one rod-shaped body is surrounded withat least one secondary rod-shaped body of the at least one rod-shapedbody having a smaller diameter.
 14. The cylindrical composite bodyaccording to claim 11, wherein the at least one secondary rod-shapedbody is braided, woven, cross-linked, twisted or coiled around the firstrod-shaped body.
 15. The cylindrical composite body according to claim11 having an outer surface and wherein the outer surface is covered witha hydrophilic coating.
 16. A tube-shaped composite body consisting of:at least one rod-shaped body, consisting essentially of: one or morenon-metallic filaments; a non-ferromagnetic matrix material, wherein thenon-ferromagnetic matrix material encloses and/or agglutinates the oneor more non-metallic filaments; and a multiplicity of doping particlesdistributed in the non-ferromagnetic matrix material, wherein the dopingparticles generate magnetic resonance tomography artefacts; and anon-ferromagnetic shell material, wherein the shell material enclosesand/or agglutinates the at least one rod-shaped body.
 17. Thetube-shaped composite body according to claim 16, consisting of severalrod-shaped bodies that are peripherally embedded in a radialdistribution in the rod-shaped composite body.
 18. The tube-shapedcomposite body according to claim 16, wherein the rod-shaped bodies areembedded in a regular radial distribution.
 19. The tube-shaped compositebody according to claim 16, consisting of several rod-shaped bodieswherein the rod-shaped bodies have the same or different diameters. 20.The tube-shaped composite body according to claim 16, consisting ofseveral rod-shaped bodies wherein the rod-shaped bodies are braided witheach other, woven, cross-linked, twisted or coiled.